Towards Garbage Collection Mechanism for RTSJ-Oriented Embedded Java Processor

Currently, Java has been gradually applied in embedded real-time area with the improvement by the Real-Time Specification for Java (RTSJ). Accordingly, a hardware Java execution engine for embedded real-time applications, JPOR-32 (32-bit Java Processor Optimized for RTSJ), is designed. Taking JPOR-32 for an example, this paper presents the garbage collection mechanism for RTSJ-oriented embedded processor in detail. JPOR-32 provides effective architectural support for garbage collection. And the object reference format of JPOR-32 provides supports for objects tracing and heap scanning. The support for write barrier of real-time concurrent GC is also performed. Moreover, JPOR-32 provides optimized instruction level support for garbage collection. In addition, different garbage collection algorithms are compared on the base of the resource-constrained feature and the real-time requirement of the processor, and the hybrid garbage collectors are suggested.